Why does the App Store keep asking for Verification?

Everytime I want to download a new application, App Store keeps asking me for verification on my payment info, and even though I tried to add/remove payment choices, it just prevents me from downloading anyways. After scouring for solutions, I found that it might be due to a pending purchase/subscription. However , the subscription that was causing my problems was activated and then subsequently cancelled in 5 minutes, while the app promised a 3-day free trial. I wonder if there is any way to resolve this without paying, seeing as I live in a poor country, is poor myself and still is a minor.

[Re-Titled by Moderator]